Opiate Substitutes

Opiates are relatively powerful drugs that act on the central and peripheral nervous systems to dull pain, and in higher doses can be used as anesthetics. Examples include morphine, fentanyl, oxycodone, hydrocodone, codeine, meperidine and methadone. Other classes of drugs may be used for pain management as well, though some may be more effective for specific types of pain, such as pain caused by nerve damage versus pain from inflammation.

Acetaminophen

Acetaminophen, commonly sold as Tylenol, is effective as a pain reliever for acute and chronic pain, according to the "Textbook of Anaesthesia." It may reduce the needed dosage of opiates for pain relief by 30 percent after surgery. The mechanism of action is not well understood, but it is thought to inhibit the formation of a class of signaling molecules in the brain called prostaglandins which contribute to the sensation of pain. Side effects are generally mild, but overdose can cause liver failure.

NSAIDs

NSAIDs include drugs such as aspirin and ibuprofen. One of the most powerful NSAIDs available, ketorolac, is nearly as strong as opiates. NSAIDs inhibit enzymes called cyclooxygenase 1 and 2, thus interfering with the production of substances that cause inflammation and pain, such as prostaglandins. Side effects include stomach ulceration and bleeding, diminished platelet functioning which contributes to bleeding, and kidney damage. A similar type class of drug is called COX-2 inhibitors, but their use has been limited due to potential cardiovascular events such as strokes and heart attacks.

Other Drugs

Ketamine is an intravenous anesthetic that has analgesic effects at low doses. It is structurally similar to PCP, and interferes with a chemical transmitter in the brain called glutamate by binding to a protein which contributes to pain sensations called the NMDA receptor. It is effective in treating chronic and acute pain. Its most prominent side effect is hallucinations and nightmares. It can also increase blood pressure and heart rate.

Flupirtine has a mechanism of action similar to ketamine, and may be effective in treating fibromyalgia. It has been used for the treatment of cancer pain, post-operative pain and other pain causes.

According to MayoClinic.com, pain that is predominantly caused by nerve damage or nerve transmission problems may respond best to anticonvulsants such as pregabalin, and antidepressant drugs such as TCAs may also be effective in reducing pain in certain patients.